In the prior art, it is well known to produce composite or clad materials, especially in the field of aluminum alloys. Clad aluminum alloys are especially desirable since the aluminum can be combined with another material serving a different purpose. For example, aluminum alloys are clad with a brazing material which is of a lower melting point to form a brazing sheet.
In one prior art technique, the brazing sheet is formed by first bonding the brazing material to a core material at an ingot or slab stage. The clad ingot must then be subsequently hot worked and cold worked to a final gauge. During the hot working, surface oxides are often formed, the surface oxides adversely affecting the brazing performance of the final product.
As an alternative, the prior art has produced clad aluminum materials by first casting and rolling a material to be used as the brazing component into thin gauge liner stock. The thin gauge liner stock is then bonded to an aluminum core strip material, the bonding typically occurring during continuous casting of the strip core material. This processing is also not without drawbacks since care must be taken to assure that the liquid core material adheres to the liner stock during the casting/bonding step.
In view of the disadvantages noted above with respect to prior art cladding techniques, a need has developed to provide improved methods and apparatus for cladding materials, particularly aluminum materials. In response to this need, the present invention provides a method and apparatus for producing a clad stock material which overcomes the disadvantages noted above by simultaneously hot working and roll bonding a continuously cast material and a liner stock to be clad thereon.